Process for preservation of metal surfaces



Patented Sept. 13, 1932 UNITED STATES PATENT OFFICE CHARLES A. VAN D'USEN AND LOUIS HAASE, OF BALTIMORE, MARYLAND, ASMGNORS TO THE GLENN L. MARTIN 00., OF BALTIMORE, MARYLAND, A CORPORATION 01 MARY- LAND PROCESS FOR PRESERVATION OI METAL SURFACES No Drawing. Application filed June 80,

Our invention relates to protective coatings for certain metals which are subject to corrosion.

" them with suflicient tenacity to constitute an effective resistant to corrosion. The film forming properties of the metal havebeen utilized to a considerable extent as a means. for resisting the tendency of the underlying metal to corrode but difficulties arise in the initial application of an effectively adhesive coating of paint to the film, or 1n servlce renewal of the coating. A roughened surface such as that obtained by sanding, or by the electrolytic formation of an anodic film, is inadequate to retain a coating of paint for a. satisfactory period of time.

lVe have discovered that conventional mlxtures do not penetrate the pores of an electrolytic film because they do not possess the property of wetting a material of its molecular nature, a fact which accounts for the failure to obtain an adequate foundation anchorage for an adhesive coat of paint.

The principle object of our invention is to increase the corrosion resisting properties of an anodic film.

Another object is to provide a foundation upon which to apply a tenacious coat of paint to aluminum or aluminum alloy surfaces.

Another object is to reduce the intensive effort heretofore required in an attempt to apply an adhesive coat of paint to a metal containing aluminum,

Another object is to prolong the useful life of aluminum and aluminum alloy parts in service by facilitating the renewal of a paint 1980. Serial No. 485,057.

surface by subsequent applications of conventional mixtures.

The objectives as enumerated are met by our process which will now be described whereby those skilled in allied arts will be enabled to obtain the results as claimed.

The fabricated members to be processed are cleaned of foreign matter by conventional methods one of which is by the action of hot alkaline solutions.

Immediately after cleaning, the parts are electrolytically treated by conventional methods one of which is to subject the parts to electrical conduction in a solution of a chromic acid nature, or in phosphate solutiqns, which methods are well known in the ar Immediately after formation of the film, the parts are thoroughly rinsed in hot water to remove the residue of electrolyte and to dry the pores of the anodic film.

Immediately after drying, bitumen dissolved in benzol to a high viscosity is applied to the virgin film. We have discovered that benzol as a solvent has the property of carrying a bituminous material into the minute fissures or pores of the film, and that saturation of the film with bitumen is intensified by manual manipulation of the overlying mass in contact with the film. Benzol is particularly satisfactory for our purpose because, in addition to its film wetting characteristic, it evaporates rapidly during manipulation at ordinary atmospheric temperatures and therefore conserves time for carrying out the process. The unabsorbed portion of bitumen is removed by continued manipulation anodic film from the underlyin metal. Cori- -Abrasions which cutthrough the paint and the film can be effectively protected by the application of an overlying coating of paint which effectively bridges the gap 1n the film and anchors to the adjacent bituminated film or to the painted film.

We use the term benzol to indicate a solventthe chemical nature of which issuc'h as to wet, and therefore to penetrate, an anodic film as contrasted to solvents which do not possess that property. Benzol. substitutes which possess the properties of dissolving bitumen and of wetting an anodic film can be made without departing from the spirit of our invention.

What we claim is a 4 1. The process for protecting predominantly aluminum surfaces against atmospheric corrosion which consists of forming thereon an anodic film; hot cleansing said filmed surfaces; applying a film wetting bituminous material to said film; manipulating said material into the pores of said film; removing the overlying material from said film 2. The process forv protecting predominantly aluminum surfaces against atmos pheric corrosion which consists of forming thereon an anodic film; hot cleansing said filmed surfaces; applying benzolated bitumen to said film; compacting said bitumen .into the pores of said film; removing the overlying bitumen from said film.

' 3. The process for protecting the surfaces of anodically filmed metals which consists of hot cleaning said filmed metals; applying bitumen dissolved in an anodic film wetting solvent to said film; rubbing the solution into said film; rubbing the excessof said solution from the surface of said film; evaporating said solvent from said film; and applying a coat of paint primer to the bituminated film.

4. The process for protecting the surfaces of anodically filmed metals which consists in cleaning said metals; applying bitumen dissolved in an anodic film wetting solvent; manipulating said bitumen into said film removing the excess of said bituminous solution from the surface of said film by continuing the manipulating operation While evaporating said solvent; applying a primer mate rial to said bituminated film; and applying protective paint coatings to said primer material. 1

. 5. The process of protecting the surfaces of aluminum alloys against atmospheric corv rosion which consists in the formation there- 'on of an anodic film; hot cleansing said film;

saturating said film with bitumen dissolved in benzol; mechanically massaging said bituminous solution into intimate relation with said film; rubbing the excess of said solution from the surface of said film; evaporating sald benzol from said film and. applying a coat of paint to said dried bituminated filmed surface.

6. The process of protecting the surfaces of aluminum alloys against atmospheric corros1on which consists in the formation thereon of an anodic film; hot cleansing said film; applying bitumen dissolved in benzol to said film; mechanically massaging said bituminous solution into intimate relation with said film rubbing the excess of said solution from the surface of said film; evaporating said benzol from said film and applying a coat of primer to said driedbituminated filmed surface.

7. The process of protecting the surfaces of aluminum against atmospheric corrosion which consists in the formation thereon of an anodic film; hot cleansing said film; applying bitumen dissolved in benzol to said film; mechanically massaging said bituminous solution into intimate relation with said film; rubbing the excess of said solution from the surface of said film; evaporating said benzol from said film and applying a coat of primer to said dried bituminated filmed surface.-

8.,The process for protecting predominantly aluminum surfaces against atmospheric corrosion which consists of forming thereon an anodic film; hot cleansing said surfaces; applying benzolated bituminous material to said film; manipulating said material into the pores of said film, continuing said manipulation concurrently with evaporation of the benzol to remove the overlying material from said film.

9. A predominantly aluminum article of manufacture having a composite surface comprising an anodic film the pores of which contain bitumen, said bitumen being compacted into said pores flush with the adjacent impervious and exposed portions of said film.

10. A predominantly aluminum article of manufacture having a composite film surface comprising anodic oxide and bitumen, said bitumen compacted into the pores of said oxide substantially flush with the impervious outer surface portions of said film.

11. A predominantly aluminum article of manufacture having a composite surface comprising an anodic film the pores of which contain compacted bitumen, and the film portions adjacent said pores being free from bituminous residue.

12. An article of manufacture including predominantly aluminum base metal having a composite surface comprising an anodic film theores of which contain bitumen .substaintia y-free .from voids, and the exposed surfacesv of-Jsaid bitumen lying substantially flush 'with the impervious portions of the outer surface'of said film.

In testimonywhereof; we hereunto afiix our signatures.

LOUIS .HAASE.

VAN DUSEN. 

